A study of the disordered dilute magneticsemiconductors Zn_(1-x)Cr_XSe andZn_(1-x)Fe_xSe

摘要

We report on the electronic structure and exchange interactions in the dilute magneticsemiconductors Zn_(1-x)Cr_xSe and Zn_(1-x)Fe_xSe. The exchange energies and densities of stateswere obtained using the layer Korringa–Kohn–Rostoker method and the coherent potentialapproximation. We find that the dominant exchange in all cases is the super-exchangemechanism, and it is found to be antiferromagnetic for Zn_(1-x)Fe_xSe at all concentrations. ForZn_(1-x)Cr_xSe the exchange interaction changes from ferromagnetic to antiferromagnetic at highconcentrations due to the ability of Cr in the antiferromagnetic state to more effectively bondwith the host structure. The strength of the super-exchange coupling in the tight binding modelis linear in concentration, which we observe for Zn_(1-x)Fe_xSe. However, as in the case ofZn_(1-x)Cr_xSe, when the chemical and magnetic interactions are strongly coupled this simplescaling is no longer observed.